Re: emacs reproducible builds part1 of 2 : eln

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 11 Jan 2024 22:17:24 +0100
> From: "Bernhard M. Wiedemann" <bernhardout@lsmod.de>
> 
> I'm working on reproducible builds for openSUSE
> and in that process found that our emacs-29.1
> package varies across builds from 2 different issues
> 
> The diff is visible at
> https://rb.zq1.de/compare.factory-20231231/diffs/emacs-compare.out
> 
> Here is a simple reproducer that works in our build env:
> 
> cd ~/rpmbuild/BUILD/emacs-29.1/native-lisp &&
>   for i in $(seq 10) ; do
>    ../src/emacs -batch \
>    --eval "(batch-native-compile t)" ../lisp/term/x-win.el &&
>    md5sum 29.1-70b784e9/x-win-3c49581f-6ddb7e08.eln
>   done | sort | uniq -c
> 
> 
> That prints variations of
>        6 0c749bdbef8d9fa7b1afc2f042caf45b 
> 29.1-70b784e9/x-win-3c49581f-6ddb7e08.eln
>        2 3022ea8c675b69ac79005281fd824179 
> 29.1-70b784e9/x-win-3c49581f-6ddb7e08.eln
>        2 57bc581456c38395e9ac6409bbcb0d6e 
> 29.1-70b784e9/x-win-3c49581f-6ddb7e08.eln
> 
> 
> while the same with setarch -R ../src/emacs
> produces deterministic
>       10 0c749bdbef8d9fa7b1afc2f042caf45b 
> 29.1-70b784e9/x-win-3c49581f-6ddb7e08.eln
> 
> So somewhere in the batch-native-compile code is a place that adds 
> ASLR-related non-determinism into the .eln file. From the diff, it 
> probably is some ordering issue.
> 
> I'd appreciate pointers to where that non-determinism gets added and how 
> to patch it out.

Andrea, can you perhaps help Bernhard understand where the differences
come from?